At present, a monitoring lens (namely, CCTV (Closed Circuit Television) Lens, namely, a lens for use in a closed circuit television) requires a rather large vision field width and requires a rather high resolution for a monitored object or person and day-and-night dual use function. However, the former two aspects conflict with each other because a system needs to have a very long focal distance to clearly distinguish details of the monitored subject. It is impossible to implement an optical system which has an extremely large vision field and a rather long focal distance at the same time. Therefore, zoom is introduced to meet the needs of the two aspects, i.e., a short focal distance is used to achieve a large vision field, and the short focal distance is shifted to a long focal distance when an object or person to be tracked and monitored is found, to obtain more information about details.
However, the current monitoring lens has problems such as a short focal distance and a low zooming ratio. In addition, other objects, desirable features and characteristics will become apparent from the subsequent summary and detailed description, and the appended claims, taken in conjunction with the accompanying drawings and this background.